Method for coding and decoding digital data stored or transmitted according to the pixels method for transmitting prioritised pixels

ABSTRACT

A method for coding and decoding digital data stored or transmitted according to the pixels method for transmitting prioritized pixels. The content of the information to the coded or decoded consists of individual pixel groups. Each pixel group comprises a place value, at least one pixel value and a priority value assigned thereto. At least one key which makes possible to code or decode the place value and/or the pixel value or values of the pixel group is used. The most varied needs can be taken into consideration during the coding in terms of used keys and coded parts of information, for example the place values and/or the pixel group values.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention comprises a process to code and decode digital datatransmitted or stored via the prioritized pixel transmission methodaccording to the preamble of patent claim 1.

2. Discussion of Related Art

The creation of informational content, such as pictures, videos, audiodata and documents, is very complex. In the transmission and storage ofsuch informational content, in many applications it is sensible andnecessary to code the information in order to protect it againstunauthorized access. To this end, there are a series of coding methodsand applications that meet this need.

In the process, coding of information can be done at various levels.

-   -   Directly in an application, for example using code word        protection in personal computers or for access to a program    -   Independent of an application, for example by means of the        well-known PGP encoding method in the case of E-mail        applications    -   During the transmission of the information, for example the        transmission of information over the Internet, using IPSec        (Internet Protocol Security).

Prior art coding methods do not have the ability to code the informationflexibly and scalably. This means that there isn't any way to flexiblyadjust coding processes according to the information content and thespecific applications. Such flexibility can, however be sensible if itis desired to offer video on demand, for example, wherein different feesare to be assessed for different video qualities, for example in as afunction of the screen resolution.

SUMMARY OF THE INVENTION

The One object of the invention is to provide a method for coding anddecoding of digital data transmitted or stored according to theprioritized pixel transmission method, thereby making it possible tocode the information flexibly and scalably.

This object is met according to the invention by the features of patentclaim 1.

The bases for the process according to the invention include the methodsof compression and decompression of picture and video data usingprioritized pixel transmission as described in the German patentapplications DE 101 13 880.6 (corresponding to PCT/DE02/00987) and DE101 52 612.1 (corresponding to PCT/DE02/00995). In these methods, thedigital data processed, for example image or video data, consist of anarray of individual image points (pixels), wherein each pixel contains apixel value, which can change over time, that provides information onthe color or brightness of the pixel. According to the invention, eachpixel or pixel group is assigned a priority, and the pixels are filed ina priority array according to their prioritization. At any given time,this array contains the pixel values sorted according to thisprioritization. These pixels and the pixel values used for thecalculation of their prioritization are transmitted or stored accordingto the prioritization. A pixel receives a high priority if thedifference from its adjacent pixel is very large. During reconstruction,the current pixel values are shown on the display. The pixels that havestill not been transmitted are calculated from the pixels alreadytransmitted.

The disclosure of applications DE 101 13 880.6 and DE 101 52 612.1should be included in their entirety in the disclosure of thisinvention.

According to this invention, the transmission and storage of theprioritized pixel groups is done in the form of data packets, whereinthe data packets can contain not just image data in the form of imagepoints (pixels), but can contain any type of digital data that can bestored in an array. The data packet consists of a data value thatdescribed the position of the pixel group in the array and also containsthe values of the individual pixels of the pixel group. By coding thepositional value of the pixel group and/or the pixel values of the pixelgroup, it becomes possible to protect the data contents againstunauthorized access. Depending on the keys used and on which portions ofthe information content are coded, for example positional values and/orpixel group values, a wide variety of coding needs can be met. The datapackets are transmitted and/or stored in descending order according toimportance. Thus, according to the invention it is possible to code anddecode the pixel groups according to their importance, at least forstatic, temporally unchanging n-dimensional arrays.

The advantage of the invention compared to the current state of the artis in the scalable manipulation of the coding method. In contrast tousual methods, separately coding the positional values and/or pixelgroup values offers the advantage that this becomes the only methodnecessary to incorporate into the respective applications and deviceswhen different requirements arise. Once this method is implemented, awide variety of requirements can utilize the same method. This educesthe number of implementations, which among other things saves memoryspace, which is of limited availability, particularly for mobile endusers. The reduction of the number of implementations is due to theability to code audio, image and video data with the same method.

Advantageous embodiments and further developments of the invention areindicated in the subordinate claims.

BRIEF DESCRIPTION OF THE DRAWING

Short description of the drawings:

FIG. 1: A representation of an image array made up of 20×21 pixels;

FIG. 2: A representation of various forms of pixel groups;

FIG. 3: A newly generated image array with pixel groups inserted in thecorners of the image;

FIG. 4: A Filling in the surfaces between the pixel groups alreadyinserted;

FIG. 5: A Inserting more pixel groups and filling in the intermediatesurfaces.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A few exemplary embodiments of the invention are explained below.

It is assumed that the information content exists as a 2-dimensionalimage file (image array). Each image point (pixel) of the image array isrepresented by a 32 Bit value (pixel value), for example. The 32 Bitsare divided into 4 values (transparent, red, green, blue), each with 8Bits. The image points of the image array are enumerated, with theposition of each pixel being given a whole number value. Pixel groupsare formed consisting of a reference pixel that indicates the positionof the pixel group within the array, and other pixels that surround thereference pixel. Each pixel group is assigned a priority depending onits “image importance”, with the pixel groups with the highest prioritybeing stored or transmitted first.

The pixel groups can now be transmitted or stored at different codinglevels according to the invention.

No Coding:

Free access to all information content, i.e. the pixel groups aretransmitted in un-coded form.

Use of a Simple Key:

A single key is used to code and decode, i.e. a symmetric coding processis used. In this method for example, the positional values of thereference pixels of a pixel group can be coded so that without the rightkey, it is impossible to place the pixel groups in the right position inthe image array. The key can be transmitted via a second transmissionpath, for example via Email or regular mail. No other infrastructure isnecessary. A symmetric coding method is faster than an asymmetric methodsuch as PGP.

Use of an asymmetric coding method: a private and public key are used tocode and decode the information content, respectively. The coding iscomplex compared to symmetric methods, and is limited to onlypoint-to-point relationships. However, it is not necessary to transmitthe key via a second transmission path.

Use of a Multiple Key:

A multiple is made up of a combination of individual keys. The keys canbe dependent on information content, on time, original source, ontransmission medium or on other features.

This allows the playback of information content to be limitedarbitrarily as needed, allowing the information to be displayedaccording to the situation. Here are a few examples:

-   -   Temporal components in the key: The information content can only        be decoded beginning at/by a specific time point.    -   Key is dependent on the transmission medium: The information        content can only be decoded if the transmission medium has a        specific identification.    -   Key dependent on the original source: The information content        can only be decoded at, for example, the device that recorded it        in order to provide protection against misuse when creating        backup copies.        Use of Cascaded Keys:

Cascaded keys can be used to partially encode the information content.For example, this method can be applied to transmit a normal quality incoded form and a poor quality, for example for a pictorial preview, inun-coded form in the same data stream without any consequent redundancy.Such redundancy can, for example, reduce the resolution of a picture. Inthis context, “resolution” does not mean “picture height×picture width”,since this parameter doesn't change when using this method. Rather, areduction in resolution indicates a deviation in the original image,which can occur during reconstruction because of pixel groups that havenot yet been transmitted and/or decoded. The method of cascaded keysworks according to the principle of the onion layer. For example, inusing the method of prioritized pixel transmission, the pixel group sizecan be reduced to create a cascaded keying sequence. A pixel groupconsists of a (reference) pixel that is clearly specified by itspositional value, and a number of other pixels. For example, if a pixelgroup consists of a total of 9 pixels, 5 pixels can be transmitted inun-coded form and 4 pixels can be transmitted in coded for. The outerlayer that includes the 5 un-coded pixels contains no coding and wouldpermit the viewing of a video at postage stamp size without a key, forexample. At the next layer, one or more of the coded pixels aretransmitted. For each further layer, another key is used. The type oflayer is agreed upon between sender and receiver prior to thetransmission. In this way, whoever has all the keys and can decode allthe layers can view the video in the best quality.

In order to reduce disruptions that can arise as a result of, forexample, dependencies between the data of the individual layers, a hashvalue can be transmitted along with the positional value and the valuesof the pixel groups in this type of coding. This hash value iscalculated from the positional value and the values of the pixel groups.If the hash value calculated in the receiver does not agree with thetransmitted hash value, these pixel groups are not decoded. Thisprevents any disruptions from other layers from occurring.

It is possible to combine the different keys and methods.

Of course, the coding method according to the invention is not justapplicable to image and video data, but also to all types of digitaldata that can be subdivided into data blocks, similar to the data blocksof image points.

This invention is explained in more detail below with the help of asimple example.

In Table 1, a portion of a data stream is shown that was preparedaccording to the prioritized pixel transmission method. The value “Posx” indicates the respective position of the pixel group, “Px_n”indicates the individual pixel values of the pixels contained in thepixel group. For example, each pixel group consists of 5 pixels. TABLE 1Pos0 P0_0 P0_1 P0_2 P0_3 P0_4 P0_5 Pos1 P1_0 P1_1 P1_2 P1_3 P1_4 P1_5

Table 2 indicates the coding of just the positional values. Advantage:only a portion of the data stream needs to be coded, which provides aclear increase in performance compared to a complete coding of all data.A reconstruction of the data so coded without knowledge of the key isnot possible, or it is only possible with a lot of computing power.TABLE 2 Pos0 P0_0 P0_1 P0_2 P0_3 P0_4 P0_5 Pos1 P1_0 P1_1 P1_2 P1_3 P1_4P1_5

Table 3 indicates the coding of part of the pixel groups. Advantage: Thesame pixel group provides different qualities of image, audio or videodata reconstruction due to differences in coding of the pixel values. Inthe example illustrated below, the receiver can use the positional valueand the pixel values Px_(—)0 through Px_(—)2 without a key. To decodethe pixel values Px_(—)3 through Px_(—)5, the correct keys are neededrespectively. If the receiver does not have the key(s) for the pixelvalues Px_(—)3 through Px_(—)5, the application must reconstruct thesepixel values from the available values Px_(—)0 through Px_(—)2. However,since the receiver is missing a number of pixel values, the quality ofthe reconstruction (resolution) is considerably reduced. TABLE 3 Pos0P0_0 P0_1 P0_2 P0_3 P0_4 P0_5 Pos1 P1_0 P1_1 P1_2 P1_3 P1_4 P1_5

In the examples illustrated, coded and un-coded data are transmitted inthe same data stream. In order to recognize transmission errors and torecognize whether the decoding was successful, each portion of the pixelgroup (position value and Px_n) can receive a CRC check in decoded form.If a transmission error occurs, and the CRC check fails, thecorresponding pixel value is not used in the reconstruction. The otherportion of the pixel group can continue to be used. In this way, therobustness of the transmission process against transmission errorsincreases at the same time. Instead of a CRC check, hash functions canbe used. These offer better backup protection, but require morecomputing power.

1-8. (canceled)
 9. A method to code and decode digital data transmittedor stored according to the prioritized pixel transmission method,wherein the information to be coded or decoded comprises individualpixel groups, wherein each pixel group has a positional value, at leastone pixel value, and a priority value assigned to it, said methodcomprising at least one key used with which the positional value and/orthe pixel value/pixel values of a pixel group are selectively coded ordecoded.
 10. The method according to claim 9, wherein the key isselectively linked to the type of information content to be coded and/orto the original source, and/or to the transmission medium used, or itcontains a temporal relationship.
 11. The method according to claim 9,wherein each pixel value, or one or more selected pixel values, arecoded or decoded using its own separate key.
 12. The method according toclaim 10, wherein each pixel value, or one or more selected pixelvalues, are coded or decoded using its own separate key.
 13. The methodaccording to claim 9, wherein a symmetrical coding method is carriedout.
 14. The method according to claim 10, wherein a symmetrical codingmethod is carried out.
 15. The method according to claim 12, wherein asymmetrical coding method is carried out.
 16. The method according toclaim 9, wherein an asymmetrical coding method is carried out.
 17. Themethod according to claim 10, wherein an asymmetrical coding method iscarried out.
 18. The method according to claim 12, wherein anasymmetrical coding method is carried out.
 19. The method according toclaim 9, wherein in that the pixel groups are comprised of digitizedscanned values of an audio signal.
 20. The method according to claim 10,wherein in that the pixel groups are comprised of digitized scannedvalues of an audio signal.
 21. The method according to claim 12, whereinin that the pixel groups are comprised of digitized scanned values of anaudio signal.
 22. The method according to claim 9, wherein the filescontain image data, video data or audio data.
 23. The method accordingto claim 12, wherein the files contain image data, video data or audiodata.
 24. The method according to claim 15, wherein the files containimage data, video data or audio data.
 25. The method according to claim21, wherein the files contain image data, video data or audio data. 26.The method according to claim 9, wherein the color level of the pixelvalues is coded or decoded in graduations using a separate key.
 27. Themethod according to claim 15, wherein the color level of the pixelvalues is coded or decoded in graduations using a separate key.
 28. Themethod according to claim 21, wherein the color level of the pixelvalues is coded or decoded in graduations using a separate key.
 29. Themethod according to claim 22, wherein the color level of the pixelvalues is coded or decoded in graduations using a separate key.